Materials Science Forum Vol. 756

Abstract: In this work, a chemically grown ZnO rod – like structure is produced via precipitation and post – sonication treatment based on the hydrolysis of zinc iodide (ZnI₂) and diethanolamine (DEA). ZnO rod – like structures with aspect ratio of 3 to 4(diameter of 235 nm and 800 nm in length) was observed from the TEM micrograph.The as-synthesized ZnO wurtzite structure was compared to sample without ultrasonic irradiation treatment to study the effect of bubble implosion on the formation of the particle. In contrast to particles treated with ultrasonic irradiation, micron sized and agglomerated particles were observed in sample without the treatment. The mechanism related to acoustic cavitations and the formation of rod – like structure is explained. The XRD results show polycrystalline structure on both samples. The optical property of ZnO was evaluated using room temperature UV - Visible absorption spectroscopy. The result showed an absorption peak at 381 nm in wavelength.

Abstract: Simple sol-gel route was used to synthesis the TiO₂ nanoparticles and examined by X-ray diffraction (XRD). The small particle size and uniform morphology of the TiO₂ were found at different calcination temperatures. The kinetic study of phase changes from the anatase to rutile using the X-ray diffraction data with Avrami equation was investigated. The transformation of anatase to rutile was started after 500 °C and above by decreasing of XRD peaks intensity of anatase with rutile increased. The activation energy of the rutile phase was found lower which indicated that uniform shape and morphology of TiO₂ nanoparticles. At same time, changes of activation energy value depended on the experimental conditions was observed.

Abstract: An ultraviolet (UV) shielding agent based on Fe-doped zinc oxide nanorods (ZnONRs) was synthesized by ex-situdoping using spray pyrolysis technique. These Fe-doped ZnO NRs could reduce the inherent photocatalytic activity of zinc oxide while still maintaining their ultraviolet filtering capability. In this work, the effect of doping duration by spray pyrolysis technique on the optical property and photocatalytic efficiency of ZnO NRs was studied. The room temperature photoluminescence (PL) analysis on the Fe-doped ZnO NRs indicates the red-shift of violet emission peak, i.e. from 378.97 nm (undoped) to 381.86 nm (60 mins.doping). Besides, the reduction of I_UV/_Vis ratio of PL reveals that the ex-situ Fe doping deteriorated the crystal quality of ZnO NRs. The photocatalytic study shows that the rate constant of Fe-doped ZnO NRs was smaller than the undoped ZnO NRs. It means that the Fe-doped ZnO NRs were less effective in degrading the RhB solution.

Abstract: The main development of ZnO nanorods (NRs) is focused on the gold catalyst and heteroepitaxial approach.However, the presence of Au may generate undesired deep level traps in the ZnO bandgap, which could be very harmful to the performance of transistors. The objective of this study is to synthesize ZnO NRs via homoepitaxial growth without using foreign catalyst by Chemical Vapour Deposition (CVD) technique. The growth of catalyst-free ZnO NWs at different CVD synthesis parameters such as amount of Zn powder, substrate location and synthesis duration on the catalyst-free ZnO NRs were studied systematically. The effect of these parameters on the size and areal density of ZnO NRs provided a better understanding on the growth mechanism of NRs via the Vapour-Solid (VS) mechanism.

Abstract: A new method for preparation of titania nanowires with diameter around 20 nmand length up more than 4um is described. The precursor was supply from local amang plant in Lahat, Perak which is produced the by product called synthetic rutiles. This precursor was mix with NaOH to form sodium titanate followed by heating at temperature of 550°C for 3 h. The sodium titanate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania nanowires during the heat treatment. The crystalline phase of the titania nanowires is rutile. The precursor as well as titania based samples were characterized by X-ray diffraction, Energy dispersive X-ray and scanning electron microscopy.

Abstract: Composite of TiO₂ nanowire and Cu₂O nanocube has been prepared. TiO₂ nanowire with ~240nm in thickness and 20 nm in length were synthesized by using liquid phase deposition(LPD) method at 50°C for 4h on ITO substrate. The anatase phase of TiO₂ nanowire was obtained by annealing the samples at 400°C for 1hin air. The Cu₂O nanocubes were prepared by the reduction of Cu²⁺ions with ascorbic acid in the present of trisodium citrate and sodium dodecilsulfat (SDS) surfactant under an alkaline condition. The SDS addition was added with various concentrations namely 10 mM, 18 mM, and 26 mM during the Cu₂O preparation for spin-coated onto TiO₂ nanowire at 3000 rpm for 30s. An optical property of TiO₂ Nanowire - Cu₂O Nanocube has been characterized by UV-Vis spectroscopy.The original TiO₂ nanowire has single absorption peak at 318 nm, but it was shifted to 321 nm as Cu₂O/SDS addition. A new peak at 440 nm was as the Cu₂O nanocube absorption spectra. The Cu₂O nanocube addition to the TiO₂ nanostructure film caused increase in the optical absorption of the system in the region 400 – 800 nm. We also studied the absorption properties of the hybrid system when Cu₂O nanocube preparation under SDS condition. It was that found the increase in the SDS concentration has caused the optical absorption of the hybrid in this region decreased. This is believed due to the decrease of Cu₂O nanocube size as the SDS concentration increase. This could be due to change in the TiO₂ nanowire-Cu₂O nanocube hybrid-structure. This cooperate may find use in photoelectrochemical application.

Abstract: Wollastonite, CaSiO₃ material was prepared from rice husk ash, as the source for SiO₂ and limestone, source for CaO using sol-gel method. Rice husk ash and CaO powder was mixed together in 100ml distilled water with the rice husk ash/CaO ratios of 45:55 and 40:60. The mixed solution was place in the autoclave and heated at 135°C for 4 hours and calcined at 950°C for 1 and 2 hours. From the XRD results,ratio of 45:55 exhibited that b-wollastonite is the major phase and the minor phase is only contributed by cristoballite and by calcining the mixture for 2hrs would yield better crystallinity. Both of the rice husk ash:CaO ratios produced wollastonite materials in cylinder structures. Wollastonite with nano size grain was obtained for an hour calcination and 2 hrs of calcination would increase the grain size over 100 nm for ratio, 45:55 and 40:60.Therefore in order to get the nano size of wollastonite material, period of calcination process has to be controlled.

Abstract: Grape-like tin dioxide (SnO₂) structures have been grown on p-type silicon (Si(100)) substrate synthesized by thermal evaporation of tin (Sn) without use of metal catalyst. The experiment were conducted in a three-zone tube furnace at a constant temperature of 1080°C,under 1.6% of oxygen (O₂) gas in an atmospheric ambient with a controlled flow rate of 1.0L/min. The prepared SnO₂ film was characterized by using X-ray diffraction diffractometer (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy(EDX) and photoluminescence (PL) measurement. The grape-like SnO₂ structures were highly crystalline with particle size (resemble grape fruit) ranging from 120-550 nm and diameter of wire (resemble grape stem) around 120-160 nm.The PL spectrum of the grape-like SnO₂ structures exhibits a broad visible light emission with a peak centered at around 623 nm, corresponding to 1.99 eV and usual near band edge emission of SnO₂ is not observed.

Abstract: A nanocrystalline CdO thin film was successfully synthesized on p-type silicon substrate with approximately 370 nm thickness by a vapor transport process (solid-vapor deposition) for Cd powder at 1274 K with argon and oxygen flows in a tube furnace. Scanning electronmicroscopy revealed that the product was a CdO nanocrystalline. X-raydiffraction and energy dispersive X-ray techniques were used to characterize structural properties. The grown nanocrystalline thin film had a grain size of 38 nm. Photoluminescence spectroscopy was conducted to investigate the optical properties of the nanocrystalline CdO thin film. A strong emission peak was observed at 511 nm (2.43 eV), which is ascribable to the near-band-edge emission of CdO with a full-width and half maximum of approximately 124 nm. The sheet resistance and the resistivity of the CdO thin film were measured using a four-point probe; R_S = 16.2 Ω/sqand ρ = 5.82×10^-4 Ω.cm.Carrier concentration and Hall mobility were obtained by Hall-effect measurement system; n = 1.53×10²⁰ cm^-3 and μ_H = 42.3cm²/Vs.